This invention relates to a plastic fastener possessing fixing legs adapted to be inserted into matched holes bored in advance in a basal object to which the fastener is to be firmly attached, and particularly to a plastic fastener so constructed as to protect the fixing legs, while in a state inserted in the holes, against an external force tending to inflict breakage upon the legs and, therefore, totally eliminate the possibility of the fixing legs being accidentally released from the basal object.
Various methods have been proposed for effecting simple union of two given objects. Particularly where the objects given to be joined are in the shape of panels, fasteners of the type having hook-shaped engaging claws provided one each at the opposite ends thereof are widely adopted. With these fasteners, the union of panels is accomplished by a procedure of inserting their engaging claws into the holes bored in advance at the corresponding positions in the opposed panels and then bringing them into fast engagement with the edges of the holes. This particular method of panel fastening enjoys a characteristic advantage that the two panels can be securely joined by such simple work as described above and the engagement, once completed with a snapping motion between the fasteners and the panels, can easily be broken whenever required. On the other hand, however, these fasteners have a disadvantage that while the snapping engagement to be obtained by their engaging claws relies to a great extent upon the elasticity possessed by the plastic material of which the fasteners are made, it has been impracticable to give the engaging portions of the fastener strength enough to provide the elasticity needed for such snapping engagement. Because of the lack of ample elasticity, there has been a possibility that, even under a slight external force, the engaging portions will sustain breakage and the fasteners themselves will accidentally come off the objects being joined therewith.
The fasteners of this type have been adopted for fastening automobile parts and have contributed much to the enhancement of the efficiency of the work of automobile assemblage. For the reason stated above, however, they have had the drawback of easily sustaining damage from impacts and vibration. Now, the fasteners will be described below as applied to the fastening of radiator grilles to automobile bodies, a particularly convenient use found for the fasteners. Since the union between the fastener and the automobile body is not restricted from the viewpoint of appearance, the engaging portions of such fasteners may be so constructed as to give them as much strength as desired. In the case of the union between the fastener and the radiator grille, however, the engaging portion of the fastener destined to come into direct engagement with the radiator grille is required to be constructed in as small a size as permissible to make it unobtrusive and to permit its easy release from engagement. The engaging portion, therefore, is not allowed to acquire the degree of strength necessary to give it the elasticity required. Since the engaging portion of the fastener on the radiator grille side is vulnerable to stress owing to its deficient strength, there are times when the fastener accidentally breaks on their radiator grille side and releases the radiator grille from its engagement with the automobile body.